Locks in which an opening code is entered by operating a plurality of buttons in a predetermined pattern have long been known in the art. Examples of such locks are shown in U.S. Pat. Nos. 3,357,216 to Cook and 3,937,046 to Wang. Such locks, however, suffer from a variety of disadvantages. It is a principal object of the present invention to overcome the disadvantages found in the prior art and to provide a pushbutton lock having advantages not heretofore obtained.
According to the present invention, there is provided a lock having a plurality of elongated buttons, each of which has a first latching member and defines on the sides thereof a plurality of gates spaced angularly and longitudinally from one another. A case contains the lock and defines a plurality of bores within which the buttons travel. The buttons are urged out a front cover of the case by biasing springs. A plurality of second latching members cooperate with the first latching members for latching the buttons in a second, depressed position against the force of the biasing springs when the buttons are pushed in by an operator of the lock.
The lock includes a locking bolt which is coupled to a checker plate. The checker plate defines a plurality of edges that engage the sides of the buttons and are received in the gates therein if the buttons are properly positioned. The checker plate is slidably mounted in a track within the case and is normally urged to a first end of the track by another biasing spring. When the checker is at this first end of its travel, the bolt is in its locking position.
A knob is coupled to the checker plate and can be operated to urge the checker plate towards a second end of its track. However, the checker plate is prevented from moving to the second end of its track if the portions of the buttons engaged by the edges of the checker plate do not include gates. By this arrangement, all of the buttons must be properly positioned, both angularly and longitudinally, if the checker plate is to be moved to its second position so as to move the bolt to the unlocking position. The provision of ten button assemblies in the illustrated embodiment yields a total of 1024 possible opening combinations, with each additional button that may be added further doubling this number.